Betacoronavirus

Betacoronavirus (β-CoVs or Beta-CoVs) is one of four genera (Alpha-, Beta-, Gamma-, and Delta-) of coronaviruses. Member viruses are enveloped, positive-strand RNA viruses that infect mammals (of which humans are part). The natural reservoir for betacoronaviruses are bats and rodents. Rodents are the reservoir for the subgenus Embecovirus, while bats are the reservoir for the other subgenera.[1]

This article is about the genus of coronavirus. Not to be confused with the Beta variant of the SARS-CoV-2 virus that causes COVID-19.
Betacoronavirus
Murine coronavirus (MHV) virion electron micrograph, schematic structure, and genome
Virus classification
(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum: Pisuviricota
Class: Pisoniviricetes
Order: Nidovirales
Family: Coronaviridae
Subfamily: Orthocoronavirinae
Genus: Betacoronavirus
Subgenera and species

See text

The coronavirus genera are each composed of varying viral lineages with the betacoronavirus genus containing four such lineages: A, B, C, D. In older literature, this genus is also known as "group 2 coronaviruses". The genus is in the subfamily Orthocoronavirinae in the family Coronaviridae, of the order Nidovirales.

The betacoronaviruses of the greatest clinical importance concerning humans are OC43 and HKU1 (which can cause the common cold) of lineage A, SARS-CoV and SARS-CoV-2 (which causes the disease COVID-19) of lineage B,[2] and MERS-CoV of lineage C. MERS-CoV is the first betacoronavirus belonging to lineage C that is known to infect humans.[3][4]

Etymology

The name "betacoronavirus" is derived from Ancient Greek βῆτα (bē̂ta, "the second letter of the Greek alphabet"), and κορώνη (korṓnē, “garland, wreath”), meaning crown, which describes the appearance of the surface projections seen under electron microscopy that resemble a solar corona. This morphology is created by the viral spike (S) peplomers, which are proteins that populate the surface of the virus and determine host tropism. The order Nidovirales is named for the Latin nidus, which means 'nest'. It refers to this order's production of a 3′-coterminal nested set of subgenomic mRNAs during infection.[5]

Structure
MERS-CoV: structure, attachment, entrance, and genomic composition

Several structures of the spike proteins have been resolved. The receptor binding domain in the alpha- and betacoronavirus spike protein is cataloged as InterPro: IPR018548.[6] The spike protein, a type 1 fusion machine, assembles into a trimer (PDB: 3jcl, 6acg​); its core structure resembles that of paramyxovirus F (fusion) proteins.[7] The receptor usage is not very conserved; for example, among Sarbecovirus, only a sub-lineage containing SARS share the ACE2 receptor.

The viruses of subgenera Embecovirus differ from all others in the genus in that they have an additional shorter (8 nm) spike-like protein called hemagglutinin esterase (HE) (P15776). It is believed to have been acquired from influenza C virus.[5][8]

Genome
Genomes of alphacoronaviruses and betacoronaviruses

Coronaviruses have a large genome size that ranges from 26 to 32 kilobases. The overall structure of β-CoV genome is similar to that of other CoVs, with an ORF1ab replicase polyprotein (rep, pp1ab) preceding other elements. This polyprotein is cleaved into 16 nonstructural proteins (see UniProt annotation of SARS rep, P0C6X7).

As of May 2013, GenBank has 46 published complete genomes of the α- (group 1), β- (group 2), γ- (group 3), and δ- (group 4) CoVs.[9]

Recombination

Genetic recombination can occur when two or more viral genomes are present in the same host cell. The dromedary camel Beta-CoV HKU23 exhibits genetic diversity in the African camel population.[10] Contributing to this diversity are several recombination events that had taken place in the past between closely related betacoronaviruses of the subgenus Embecovirus.[10] Also the betacoronavirus, Human SARS-CoV, appears to have had a complex history of recombination between ancestral coronaviruses that were hosted in several different animal groups.[11][12]

Pathogenesis
Replication cycle of viruses of genus Betacoronavirus

Alpha- and betacoronaviruses mainly infect bats, but they also infect other species like humans, camels, and rodents.[13][14][15][16] Betacoronaviruses that have caused epidemics in humans generally induce fever and respiratory symptoms. They include:

Classification
Phylogenetic tree of the lineages of genus Betacoronavirus with detail for SARS-CoV and MERS-CoV

Within the genus Betacoronavirus (Group 2 CoV), four subgenera or lineages (A, B, C, and D) have traditionally been recognized.[5] The four lineages have also been named using Greek letters or numerically.[9] A fifth subgenus, Hibecovirus, was added more recently.[17] Member subgenera and species include:[18]

Embecovirus (lineage A)
Main article: Embecovirus

Betacoronavirus 1

China Rattus coronavirus HKU24
Human coronavirus HKU1
Murine coronavirus

Myodes coronavirus 2JL14

Sarbecovirus (lineage B)
Main article: Sarbecovirus

Severe acute respiratory syndrome–related coronavirus (SARSr-CoV or SARS-CoV)

Coronaviruses
Types
Diseases
Vaccines
Epidemics and pandemics
See also

Merbecovirus (lineage C)

Hedgehog coronavirus 1
Middle East respiratory syndrome-related coronavirus (MERS-CoV)
Pipistrellus bat coronavirus HKU5
Tylonycteris bat coronavirus HKU4

Nobecovirus (lineage D)
Main article: Nobecovirus

Eidolon bat coronavirus C704
Rousettus bat coronavirus GCCDC1
Rousettus bat coronavirus HKU9

Hibecovirus
Main article: Hibecovirus

Bat Hp-betacoronavirus Zhejiang2013

See also
  • Animal viruses

References
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  2. "Phylogeny of SARS-like betacoronaviruses". nextstrain. Retrieved 18 January 2020.
  3. ProMED. MERS-CoV–Eastern Mediterranean (06) (http://www.promedmail.org/)
  4. Memish, Z. A.; Zumla, A. I.; Al-Hakeem, R. F.; Al-Rabeeah, A. A.; Stephens, G. M. (2013). "Family Cluster of Middle East Respiratory Syndrome Coronavirus Infections". New England Journal of Medicine. 368 (26): 2487–94. doi:10.1056/NEJMoa1303729. PMID 23718156.
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  7. Walls, Alexandra C.; Tortorici, M. Alejandra; Bosch, Berend-Jan; Frenz, Brandon; Rottier, Peter J. M.; DiMaio, Frank; Rey, Félix A.; Veesler, David (8 February 2016). "Cryo-electron microscopy structure of a coronavirus spike glycoprotein trimer". Nature. 531 (7592): 114–117. Bibcode:2016Natur.531..114W. doi:10.1038/nature16988. PMC 5018210. PMID 26855426.
  8. Bakkers, Mark J. G.; Lang, Yifei; Feitsma, Louris J.; Hulswit, Ruben J. G.; Poot, Stefanie A. H. de; Vliet, Arno L. W. van; Margine, Irina; Groot-Mijnes, Jolanda D. F. de; Kuppeveld, Frank J. M. van; Langereis, Martijn A.; Huizinga, Eric G. (2017-03-08). "Betacoronavirus Adaptation to Humans Involved Progressive Loss of Hemagglutinin-Esterase Lectin Activity". Cell Host & Microbe. 21 (3): 356–366. doi:10.1016/j.chom.2017.02.008. ISSN 1931-3128. PMC 7104930. PMID 28279346.
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  11. Stanhope MJ, Brown JR, Amrine-Madsen H. Evidence from the evolutionary analysis of nucleotide sequences for a recombinant history of SARS-CoV. Infect Genet Evol. 2004 Mar;4(1):15-9. PMID 15019585
  12. Zhang XW, Yap YL, Danchin A. Testing the hypothesis of a recombinant origin of the SARS-associated coronavirus. Arch Virol. 2005 Jan;150(1):1-20. Epub 2004 Oct 11. PMID 15480857
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  14. Lau, S. K.; Woo, P. C.; Yip, C. C.; Fan, R. Y.; Huang, Y.; Wang, M.; Guo, R.; Lam, C. S.; Tsang, A. K.; Lai, K. K.; Chan, K. H.; Che, X. Y.; Zheng, B. J.; Yuen, K. Y. (2012). "Isolation and characterization of a novel Betacoronavirus subgroup A coronavirus, rabbit coronavirus HKU14, from domestic rabbits". Journal of Virology. 86 (10): 5481–96. doi:10.1128/JVI.06927-11. PMC 3347282. PMID 22398294.
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  16. Zhang, Wei; Zheng, Xiao-Shuang; Agwanda, Bernard; Ommeh, Sheila; Zhao, Kai; Lichoti, Jacqueline; Wang, Ning; Chen, Jing; Li, Bei; Yang, Xing-Lou; Mani, Shailendra; Ngeiywa, Kisa-Juma; Zhu, Yan; Hu, Ben; Onyuok, Samson Omondi; Yan, Bing; Anderson, Danielle E.; Wang, Lin-Fa; Zhou, Peng; Shi, Zheng-Li (24 October 2019). "Serological evidence of MERS-CoV and HKU8-related CoV co-infection in Kenyan camels". Emerging Microbes & Infections. 8 (1): 1528–1534. doi:10.1080/22221751.2019.1679610. PMC 6818114. PMID 31645223.
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